1. Field of the Invention
The present invention relates to video image recording methods and devices, and more particularly to video image recording apparatus of the type adapted to receive input video signals from host video signal generating devices and to photographically record video images corresponding to selected portions thereof, and the methods executed by such devices and the operators thereof.
2. Description of the Prior Art
Video image recording methods and devices for photographically recording, seriatim, selected pluralities of the images borne by input video signals on x-ray type sheet film or the like in predetermined collocation are known in the prior art. For example, a video image recording device of this type is shown and described in U.S. Pat. No. 4,027,315, issued to Howard Hunter Barney on May 31, 1977.
Such prior art video image recording methods and devices have in general been characterized by the problem of "recorded image drift", i.e., changes over time in the relationship between the density of any particular photographically recorded pixel or image element and the magnitude of the corresponding portion of the input video signal, due to thermal variations in component values, component aging, line voltage fluctuations, and other equipment variables, the control of all of which is not economically feasible.
Prior art video image recording methods and devices have attempted to deal with the recorded image drift problem, e.g., by varying the exposure time, the lens aperture, or the mean light output of the internal monitor in accordance with the brightness of the image produced on the monitor screen by an internally generated, single-valued signal applied to the monitor cathode ray tube control grid, which internally generated signal was not a function of the input video signal.
Further, the image parameter control means of such prior art video image recording devices have in general merely been monitor brightness and contrast controls which in the manner common to broadcast television monitors were uncalibrated.
Some prior art video image recording devices of this type have been provided with simple photometers arranged to "view" part of the monitor screen and externally accessible pushbuttons, automatic devices, or the like for applying a fixed-level, internally generated signal to the monitor cathode ray tube control grid while the photometer output signal is read on an externally viewable meter.
Despite the provision of these expedients, however, the operation of such prior art video image recording devices has involved the carrying out of expensive, time-consuming manual calibration procedures (analogous to the monitor aligning procedures established in European Broadcasting Union technical recommendation E.B.U.R. 23-1980(E) and ASMPTE recommended practice RP71-1977, in the course of which recordings are made at various image parameter control settings and those recordings developed and cross-compared by the human operator to determine which image parameter control settings produce the desired density and photographic contrast in the recorded images.
Related Art
The documents listed immediately below contain information which is or might be considered to be material to the examination of this patent application.
U.S. Pat. No. 3,852,602 PA0 U.S. Pat. No. 4,027,315 PA0 German Offenlegungsschrift No. 2,303,800 PA0 "Ultrasound Backgrounds Black or White?" by Margaret R. Gasson, page 24, et seq., Radiology Today, February-March, 1980.
No representation is made that any of the above-listed documents is part of the prior art, or that a search has been made, or that no more pertinent information exists.